Hello sir ....try steam inhalations every day 2 times and also keep changing ur filters from time to time, If it is troubling you even , visit a doc, to get evaluated for sinusitis , Deviated septum and other things

Small workouts (exercises), avoid cool items, steaming also helping, balanced diet will help to boost immunity

You need to take first of all have good diet to improve your immune system and to have plenty of fluids. Take steam two times a day which will help improve your nasal breathing and decrease the frequency of cold and Also do breathing exercises of nose like alternate inhalation and exhalation. avoid sitting in front of the Ac that also increases the frequency of cold.